Quad Power Amps that invert phase

[Light Dependant Resistor]

Here is a list of Quad power amps that invert phase, and ones that do not

Inverts
303, 405

Non inverting
306, 606, 520f, 707, 909

The 303 as it was made for the ESL57 should be wired + to + and - to - , as normal
with the electrostatic speaker, as the speaker then corrects that phase.

With other speakers when using the 303 you need to reverse speaker polarity,
this can be quite a revelation finding this out as the sound is more open.


Cheers / Chris

[The Barbarian]

I remember an article in HiFi for Pleasure from the 80's regarding the '303' Phase reversal.

[Barry]

Useful information Chris - thanks for that.

In the past I have spent some time messing about with absolute phase, or polarity. I couldn't hear any difference so stopped worrying!

[krugdoktor]

Very interesting! Does that mean that the QUAD ESL inverts absolute phase? :scratch:

[DSJR]

Didn't the 33 preamp invert the phase as well, thereby giving correct absolute phase a the speaker terminals?

[Light Dependant Resistor]

Very interesting! Does that mean that the QUAD ESL inverts absolute phase? :scratch:

Yes applying to the ESL57 , so if using with other non inverting power amps ( checking that they are non inverting )
swap + for - but with 303 Red to Red and Black to Black

Preamps Quad 33 input stages other than disc are inverting but output also inverting inferring a overall non inverting output relative to
inputs other than disc

Quad 34 non inverting